polymer shell
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2022 ◽  
Vol 05 ◽  
Author(s):  
Wanda Jones ◽  
Bedanga Sapkota ◽  
Brian Simpson ◽  
Tarig A. Hassan ◽  
Shaik Jeelani ◽  
...  

Background: Thermoplastic expandable microspheres (TEMs) are spherical particles that consist of polymer shell encapsulating a low boiling point liquid hydrocarbon that acts as the blowing agent. When TEMs are heated at 80-190 C, the polymer shell softens and the hydrocarbon gasifies, causing the microspheres expand leading to increase in volume and decrease in density. TEMs are used in food packaging, elastomeric cool roof coatings, shoe soles, fiber and paper board, and various applications in the automotive industry. It is noted that TEMs are known by its brand name ‘Expancel’ which is also used to refer TEMs in this paper. Objective: The objective of this work was to develop and characterize forms prepared from TEMs with/without carbon nanofibers (CNFs) coatings to study the effect of CNFs on structural, thermal, and mechanical properties. Method: Sonochemical method was used to coat TEMs with various weight percentage (1, 2, and 3 %) of CNF. Neat foam (without CNF) and composite foams (TEMs coated with various wt.% of CNF) were prepared by compression molding the TEMs and TEMs-CNF composites powders. Thermal and mechanical properties of the neat and composite foams were investigated. Result: The mechanical properties of the composite foam were notably improved, which is exhibited by a 54% increase in flexural modulus and a 6% decrease in failure strain with the TEMs-(2 wt.% CNF) composite foam as compared to the neat foam. Improvement in thermal properties of composite foam was demonstrated by a 38% increase in thermal stability at 800 ºC with the TEMs-(1 wt.% CNF) composite foam as compared to the neat foam. However, no change in glass transition of TEMs was observed with the CNF coating. SEM-based analysis revealed that CNFs were well dispersed throughout the volume of the TEMs matrix forming a strong interface. Conclusions: Straightforward sonochemical method successfully triggered efficient coating of TEMs with CNFs resulting to strong adhesion interface. The mechanical properties of composite foams increased up to 2% of CNFs coating and then decreased with the higher coating presumably due to interwoven bundles and aggregation of CNFs, which might have acted as critical flaws to initiate and propagate cracking. Thermal properties of foams increased with the CNFs coating while no change in glass transition temperature was observed due to coating.


Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 62
Author(s):  
Xue Li ◽  
Peng Lou ◽  
Longquan Yang

Fe3O4@RF microspheres with different phenolic (RF) layer thicknesses are prepared by adjusting the polymerization time. With the prepared Fe3O4@RF as the precursor, Fe@C composite microspheres with rattle-like morphology are obtained through one-step controlled carbonization. This method simplifies the preparation of rattle-shaped microspheres from sandwich microspheres. Fe@C microspheres exhibit excellent microwave absorbing properties. The morphology and composition of the product are investigated depending on the effects of carbonization temperature, time and thickness of the RF layer. When the carbonization temperature is 700 °C, the carbonization time is 12 h and the polymer shell thickness is 62 nm, the inner hollow Fe3O4 is completely reduced to Fe. The absorption properties of the materials are compared before and after the reduction of Fe3O4. Both Fe@C-12 and Fe3O4@C-700 show excellent absorbing properties. When the filler content is 50%, the maximum reflection loss (RLmax) of the rattle-shaped Fe@C microspheres is −50.15 dB, and the corresponding matching thickness is 3.5 mm. At a thickness of 1.7 mm, the RLmax of Fe3O4@C-700 is −44.42 dB, which is slightly worse than that of Fe@C-12. Both dielectric loss and magnetic loss play a vital role in electromagnetic wave absorption. This work prepares rattle-shaped absorbing materials in a simple way, which has significance for guiding the construction of rattle-shaped materials.


2022 ◽  
Author(s):  
O.G. Kozhus

Abstract.The article presents the technology of covering abrasive grains with a protective polymer shell, which allows to reduce the wear of the focusing tube of the nozzle of a hydroabrasive installation. A description of the manufacturing process of a prototype abrasive with a polymer coating in a fluidized bed is presented in order to determine the critical processing modes at which a high-quality product will be obtained in a minimum operating time of the installation.


2021 ◽  
Vol 12 (4) ◽  
Author(s):  
Yu. V. Tsapko ◽  
O. Yu. Horbachova ◽  
S. M. Mazurchuk

The process of wood biological destruction is analyzed. It was found that the neglect of environmentally friendly means of bioprotection, leads to the destruction of wooden structures under the action of microorganisms. It is established that the study of wood protection conditions leads to the creation of new types of protective materials that reduce water absorption, as well as reduce the amount of substances that are the environment for the development of wood-destroying fungi. In this regard, a computational and experimental method for determining the proportion of destroyed material under the action of microorganisms using an antiseptic has been developed. The analysis of the results shows that the maximum weight loss in the case of biodegradation of untreated wood samples ranged from 7,6 to 16 %, and the weight loss of thermally modified wood samples did not exceed 3 %, antiseptic-hydrophobicizer – was less than 2 %. It was found that the protection when treated with thermally modified wood with oil-wax and azure exceeds (compared to untreated) more than 4 times in terms of biodegradation, and treatment with antiseptic-water repellent for untreated oil-wax and azure – more than 8 times. It should be noted that the presence of oil-wax and azure leads to blockage of the wood surface from the penetration of moisture or microorganisms. Therefore, the intensity of wood-destroying fungus development on the surface of various samples are differed. Obviously, such a mechanism of the protective coating influence is the factor regulating the process, which preserves the integrity of the object. On the experimental data basis and by modeling the equations, the microorganisms population dynamics in the volume of material and the function of increasing the number of dead organisms are derived. Thus, a polymer shell was created on the surface of the sample, which significantly reduced the penetration of microorganisms into the wood, and the weight loss of wood during biodegradation did not exceed 2,5 %. Additional application of protective substances on the surface increases the protection level of untreated pine wood by 72 %, thermomodified at 190 °C – 25 %, at 220 °C – by 37 %. Similar results for hornbeam wood – 60; 37 and 28 %, for oak – 50; 37 and 37 % respectively.


2021 ◽  
pp. 110887
Author(s):  
Faeze Kazemi-Andalib ◽  
Maryam Mohammadikish ◽  
Adeleh Divsalar ◽  
Unes Sahebi
Keyword(s):  

2021 ◽  
Vol 5 (10 (113)) ◽  
pp. 48-55
Author(s):  
Yuriy Tsapko ◽  
Oleksandra Horbachova ◽  
Serhii Mazurchuk ◽  
Аleksii Tsapko ◽  
Kostiantyn Sokolenko ◽  
...  

This paper reports the analysis of the biological destruction of timber and the use of protective materials, which established that the scarcity of data to explain and describe the process of bioprotection, neglect of environmentally friendly agents lead to the biodegradation of timber structures under the action of microorganisms. Devising reliable methods for studying the conditions of timber protection leads to designing new types of protective materials and application technologies. Therefore, it becomes necessary to determine the conditions for the formation of a barrier for bacteria permeability and to establish a mechanism for inhibiting material biodegradation. Given this, the dependence has been derived to determine the proportion of destroyed material under the effect of microorganisms when using an antiseptic-hydrophobicizer, which makes it possible to evaluate biopenetration. Based on the experimental data and theoretical dependences, the share of destroyed timber was determined under the effect of microorganisms, which is equal to 1 for natural timber. At the same time, this value for thermally modified timber is 0.033, and, when it is protected with oil ‒ 0.009, respectively, exposed to the action of microorganisms for 60 days. It should be noted that the presence of oil, wax, and azure leads to blocking the timber surface from penetration. Such a mechanism underlying the effect of protective coating is likely the factor in the process adjustment, due to which the integrity of the object is preserved. Thus, a polymer shell was created on the surface of the sample, significantly reducing the penetration of microorganisms inside the timber, while the loss of timber mass during biodestruction did not exceed 2.5 %. Therefore, there are grounds to assert the possibility of targeted control over the processes of timber bio-penetration by using coatings capable of forming a protective film on the surface of the material


Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2453
Author(s):  
Virginie Vergnat ◽  
Benoît Heinrich ◽  
Michel Rawiso ◽  
René Muller ◽  
Geneviève Pourroy ◽  
...  

Embedding nanoparticles (NPs) with organic shells is a way to control their aggregation behavior. Using polymers allows reaching relatively high shell thicknesses but suffers from the difficulty of obtaining regular hybrid objects at gram scale. Here, we describe a three-step synthesis in which multi-gram NP batches are first obtained by thermal decomposition, prior to their covalent grafting by an atom transfer radical polymerization (ATRP) initiator and to the controlled growing of the polymer shell. Specifically, non-aggregated iron oxide NPs with a core principally composed of γ-Fe2O3 (maghemite) and either polystyrene (PS) or polymethyl methacrylate (PMMA) shell were elaborated. The oxide cores of about 13 nm diameter were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). After the polymerization, the overall diameter reached 60 nm, as shown by small-angle neutron scattering (SANS). The behavior in solution as well as rheological properties in the molten state of the polymeric shell resemble those of star polymers. Strategies to further improve the screening of NP cores with the polymer shells are discussed.


Nanomedicine ◽  
2021 ◽  
Author(s):  
Ahmed S AbdElhamid ◽  
Dina G Zayed ◽  
Lamia Heikal ◽  
Sherine N Khattab ◽  
Omar Y Mady ◽  
...  

Polymeric nanocapsules are vesicular drug delivery systems composed of an inner oily reservoir surrounded by polymeric membranes. Nanocapsules have various advantages over other nanovesicular systems such as providing controlled drug release properties. We discuss the recent advances in polymeric shell-oily core nanocapsules, illustrating the different types of polymers used and their implementation. Nanocapsules can be utilized for many purposes, especially encapsulation of highly lipophilic drugs. They have been shown to have variable applications, especially in cancer therapy, due to the ability of the polymeric shell to direct the loaded drugs to their target sites, as well as their high internalization efficacy. Those productive applications guaranteed their high potential as drug delivery systems. However, their clinical development is still in an early stage.


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